Sf. Mcclanahan et al., Identification and consequences of distinct Loe-Silness gingival index examiner styles for the clinical assessment of gingivitis, J PERIODONT, 72(3), 2001, pp. 383-392
Background: In clinical studies, gingivitis is most frequently assessed by
the Loe-Silness gingival index (GI). The objective of this work was to deve
lop an understanding of how clinicians experienced with GI differ with resp
ect to how they apply GI and to assess the impact of different examination
styles on statistical outcomes and magnitude of treatment differences.
Methods: A method was developed to mathematically relate the average GI sco
re and degree of bleeding observed for a subject. Graphical analyses were u
sed to profile examiner styles with respect to using the GI index. A prospe
ctive single-center, examiner-blind study comparing the effects of a stagge
red prophylaxis on gingivitis was then conducted, where a difference in gin
givitis was created between two balanced groups by providing subjects a pro
phylaxis at two staggered time points. Subjects were assigned to one of two
cohorts; within each cohort, group 1 subjects received a dental prophylaxi
s following the baseline examination and group 2 subjects received a dental
prophylaxis 8 weeks later. Five to 7 days after the group 2 prophylaxis, a
ll subjects were examined for GI. Twelve experienced clinicians participate
d.
Results: Retrospective analyses indicated the presence of distinct examiner
styles which are based on the frequency that a given GI score (0, 1, 2, or
3) is measured by a clinician. In the prospective study, all 12 examiners
observed statistically significant differences between the prophylaxis trea
tment groups at the final visit for both mean number of bleeding sites and
mean GI; the magnitude ranged from 21.5% to 84.6% for mean number of bleedi
ng sites and 9.4% to 39.2% for mean GI. There were 4 distinct styles employ
ed by these experienced clinicians.
Conclusions: Varying examiner styles impact the structure of resulting data
. Importantly, the implementation of arbitrary thresholds (e.g., 20%) regar
ding percent treatment differences between groups as a guideline for judgin
g the clinical significance is scientifically unsupported. A more scientifi
c criterion in the field of gingivitis clinical testing would be the indepe
ndent demonstration of statistical superiority compared to a negative contr
ol and/or a demonstration of similar or superior efficacy to clinically pro
ven positive controls. In addition, interexaminer calibration is a mechanis
m that can be utilized to minimize the impact of different examiner styles
in clinical settings involving more than one examiner.